I know that Koa is one of the preferred woods for this instrument. However, since I already have a lot of Black Walnut boards on hand that are 1 in. thick, I thought that I might try to save some money. These boards have been in my shop for about 17 years and thus are dry and stable. Is Black Walnut stable enough for a stringed musical instrument?
I know that it is considerably softer than Koa. And I am planning to use sitka spruce for the top.
If this is a very bad idea, please let me know.

Thanks in advance!